I have three separate physical locations. Each location has a router with a static public ip address. The routers are HotBrick 1400/2, frirmware Ver 2.0 Rel 2D-b07 Build Date: Nov 7 2008, if it matters.
I have created VPNs between the 3 routers using the router firmware, location 1 uses subnet 192.168.1.0/24, location 2 uses 192.168.2.0/24, and location 3 uses 192.168.3.0/24. The VPNs are up and running - I have verified this by pinging from from the routers - I can ping both remote routers over their private ip, as well as a machine behind each router, again by private ip, from each of the 3 routers. Additionally, I can ping and make various tcp/ip connections (http, ssh, mysql) from machines at each location to various machines at the other locations.

I have 1 machine, an intel iMac running Snow Leopard (10.6.2), at 1 location, which is unable to reach any machines on the private VPNs via various network protocols (http, ping, shh). The machine can reach other machines on its same subnet, it can reach machines on the internet, but it cannot reach any machine on the private subnets of the established VPNs. It can, however, receive connections and respond to pings from machines on the VPN subnets.

I have checked that the Snow Leopard firewall is disabled, and there are no static routes set up on the router, nor anything else on the router that I can find that would block traffic from this machine to machines on the VPNs. I have rebooted the offending machine as well as the router at that location. I have changed the LAN port of the machine as well.

what does "netstat -n -r" show on the mac?
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Matt SimmonsFeb 12 '10 at 19:01

Thanks for the comment - I'm not sure what it does and what it is supposed to show - guess I'll have to research. I actually saw the answer below first and that led me to the fix.
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ScottFeb 12 '10 at 19:32

Thanks - I did not even check because I could ping the router and internet. And the machine gets a dhcp lease from the router which had the correct settings. When I went to system settings - network, all my connections showed disconnected - very curious, I could connect to internet and ping router while status showed disconnected. I set up a new location, got new DHCP lease, and everything works now. I am accepting your answer because it led me to the solution. Thanks
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ScottFeb 12 '10 at 19:27